In most welding, surfacing and cladding operations which are accomplished by the application of heat and the melting of the alloys involved, it is essential to shield the thermally excited regions with specially formulated gases. In the case of arc processes, proper selection of shielding gas which is made on the basis of the ionization potential of the gas, its density, thermal conductivity and chemical reactivity with the molten and solidified alloys, and controlled introduction of this gas about the welding region that is the arc and molten pool, guarantee predictably stable arc behavior, volumetrically sound and dimensionally consistent deposits with proper composition. This in other words minimizes alloy loss through the arc by oxidation. Similarly, many laser assisted welding, surfacing and cladding operations are affected by the gas shielding quality. For example, reactive metals such as titanium are often welded in chambers which are first evacuated or purged with inert gas because they become essentially embrittled by reaction with airborne oxygen and nitrogen.
In certain processes the absence of adequate shielding with inert gas can cause some of the superheated constituents to react with the oxygen in the air to quickly generate a violent reaction which can tend to adversely affect the process. Often this problem is solved by executing the joining process in a closed chamber purged with pure argon. However, the use of a purge chamber becomes impractical in automated processes. This is particularly true when the work cell is of a significant size and purging becomes impractical.
It is therefore an object of this invention to provide a generic shield for joining processes which is particularly well suited and mechanically compatible with an articulated arm of a robot.
It is also an object of this invention to provide a shield which can readily be employed with other arc assisted processes such as welding, surfacing and cladding.
It is yet another object of this invention to provide a generic shield which can be utilized with a laser based process.
It is a further object of this invention to provide a generic shield which is readily adapted for use with either an appropriate torch or the optics necessary for laser based metal processing.